Well... I did it, but not by choice. DH (in his infinite wisdom) decided to present me with a miniture poodle pup as a surprise when I was 7 months pregnant. 
I love dogs, but boy the timing was not ideal. It wasn't the house training, as he was sorted within a week. And luckily he doesn't shed hair, so not too much extra cleaning. And he's tiny, so doesn't need too much exercise. And I do have to admit, he's bloody adorable.
But even then he was a pretty big PITA for the first year. I didn't really have the time or energy to enjoy him at the time, which is sad. I love him now, but I would have liked to get a puppy when the girls were older and I had time to dote on him.